1. Technical Field
This disclosure relates generally to an image forming apparatus, and more particularly to an image forming apparatus using a recording head including a liquid ejection head that ejects liquid droplets.
2. Description of the Background
One example of related-art image forming apparatuses such as printers, copiers, plotters, facsimile machines, and multifunction devices having two or more of printing, copying, plotting, and facsimile functions is an inkjet recording device employing a liquid ejection recording method. The inkjet recording device includes a recording head that ejects droplets of a recording liquid such as ink onto a sheet of a recording medium while the sheet is conveyed to form an image on the sheet.
Examples of the inkjet recording device include a serial-type image forming apparatus, in which the recording head ejects liquid droplets while moving in a main scanning direction to form an image on the sheet as the sheet is moved in a sub-scanning direction perpendicular to the main scanning direction, and a line-type image forming apparatus equipped with a line-type recording head that ejects liquid droplets and does so without moving to form an image on the sheet as the sheet is moved in the sub-scanning direction.
A maintenance mechanism that maintains and recovers performance of the recording head is essential for the image forming apparatus employing the liquid ejection recording method. One of the functions of the maintenance mechanism is to discharge bubbles, foreign substances, coagulated ink, and so forth present in the recording head through nozzles in the recording head in order to prevent irregular ejection of the ink from the nozzles in the recording head.
In addition, a full-color image forming apparatus that forms full-color images using the liquid ejection recording method generally includes two separate recording heads, that is, a recording head that ejects black ink droplets (hereinafter referred to as the first recording head) and a recording head that ejects color ink droplets (hereinafter referred to as the second recording head). In such a full-color image forming apparatus, not only black ink but also color ink is ejected for maintenance of the recording heads even when monochrome printing is performed using only the first recording head, causing a waste of color ink and a concomitant cost increase.
In order to solve this problem, various techniques have been proposed. In one example, an image forming apparatus includes a scanning-type carrier which is moved reciprocally back and forth by a drive force; a first carriage that ejects black ink droplets and a second carriage that ejects color ink droplets, each detachably attachable to the carrier; a detector that detects that the carriages attached to the carrier passes through a certain reference position in a direction of movement of the carrier; and a control unit that controls movement of the carrier using as a reference a time when the detector detects the carriages.
Another example of an image forming apparatus includes carriages that eject black and color ink droplets, respectively, and a linking mechanism provided between the carriages.
In yet another approach, an image forming apparatus includes a driving head, a driven head coupled to the driving head, a first connection unit that connects the driving head and the driven head, a second connection unit that connects the driven head and a lateral plate of the apparatus, and so forth. While the driving head is moved reciprocally, the driven head coupled to the lateral plate is in a standby state. The driving head is moved to the driven head so that the driving head and the driven head are coupled to each other to reciprocally move together.
In still yet another example, an image forming apparatus includes first and second carriages detachably attachable to each other using an electromagnet. One of the first and second carriages is at a home position in a standby state while the other of the first and second carriages is moving reciprocally.
However, in the above-described image forming apparatuses, in which the carriages that respectively eject black and color ink droplets are coupled to each other in a main scanning direction with a connection unit such as the scanning-type carrier, the size of the image forming apparatus is increased in the main scanning direction by this arrangement.
FIG. 1 is a front view illustrating carriages that can be coupled to and separated from each other in a related-art image forming apparatus. The image forming apparatus includes a carriage 501 that ejects black ink droplets and a carriage 502 that ejects color ink droplets, each disposed in a main scanning direction. Each of the carriages 501 and 502 can be coupled to an intermediate scanning carrier 503 with rods 504A and 504B and grippers 505A and 505B, respectively, so that the carriages 501 and 502 are coupled to each other. Each of the grippers 505A and 505B is provided to the intermediate scanning carrier 503 and is detachably attachable to the rods 504A and 504B, respectively. When monochrome printing is performed using only the carriage 501, the carriage 502 is separated from the carriage 501 and the intermediate scanning carrier 503 as illustrated in FIG. 1. At this time, a distance a is maintained between the carriage 502 or a moisturizing mechanism 506 and a scanning range of the carriage 501 in order to prevent collision between the carriage 502 and the gripper 505B provided to the intermediate scanning carrier 503 coupled to the carriage 501, thereby increasing the width of the image forming apparatus by an amount equal to the distance α.